A number of pressure-actuated clutches and brakes are known which according to application--starting and stopping of machine elements--are grouped in separate arrangements of clutches and brakes and in combined systems. With the separately arranged clutches and brakes one normally mounts then at the opposite ends of an output shaft and provides separate connections for their actuation and cooling. Most combined arrangements with the clutch and brake at one shaft end have corresponding common actuating and coolant connections. Thus for example with the known solutions (German 2,753,534 and 2,128,242 and U.S. Pat. No. 4,006,808) of combined clutch and brake systems the clutch and brake are preferably combined at one shaft end.
Advantageous for the combined clutches and brakes are the simplified control due to only one spring-loaded actuating piston, the use of only one end of the output shaft, and the offset of the feeds of hydraulic and cooling mediums from the supply system, all at only one shaft end. The expense for sealing against other machine elements is also smaller and assembly can be simplified.
As a result of only one actuating piston the control arrangement is simplified, for example only one press safety valve is necessary. For some types of machines the one-ended mounting also changes the entire construction of the machine in a positive manner, making it more compact.
In contrast thereto there are substantial disadvantages compared to separately built clutches and brakes, on the one hand due to the increased inertia due to the construction and on the other hand to the time lost on actuation between operating the clutch and the brake as a result of the travel time of the single actuating piston. In particular with very large actuating volumes this lost time can increase the individual switchover times of the machine. In addition the output of the machine during the shift is neither held by the clutch nor by the brake which can lead for example in wedge presses to undesired travel of the ram.
Furthermore in the combined assemblies very big disks are necessary for mounting of the actuating surfaces and the springs in order to be able to accommodate these shifting elements in the assembly and to obtain a complete construction. For large torques, e.g. on forging presses, particularly expensive solutions (as in East German patent 260,111) are known for making the disks. A further disadvantage is in the limited space available for the high spring forces inside the inside periphery of the disks.